Intramolecular water-splitting reaction in single collisions of water ions with surfaces

High-Throughput Open-Air Plasma Activation of Metal-Oxide Thin Films with Low Thermal Budget

Sputter-processed oxide films are typically annealed at high temperature (activation process) to achieve stable electrical characteristics through the formation of strong metal-oxide chemical bonds. For instance, indium-gallium-zinc oxide (IGZO) films typically need a thermal treatment at 300 °C for ≥1 h as an activation process. We propose an open-air plasma treatment (OPT) to rapidly and effectively activate sputter-processed IGZO films. The OPT effectively induces metal-oxide chemical bonds in IGZO films at temperatures as low as 240 °C, with a dwell time on the order of a second. Furthermore, by controlling the plasma-processing conditions (scan speed, distance a between plasma nozzle and samples, and gas flow rate), the electrical characteristics and the microstructure of the IGZO films can be easily tuned. Finally, OPT can be utilized to implement a selective activation process. Plasma-treated IGZO thin-film transistors (TFTs) exhibit comparable electrical characteristics to those of conventionally thermal treated IGZO TFTs. Through in-depth optical, chemical, and physical characterizations, we confirm that OPT simultaneously dissociates weak chemical bonds by UV radiation and ion bombardment and re-establishes the metal-oxide network by radical reaction and OPT-induced heat.

Dynamic molecular oxygen production in cometary comae

Abundant molecular oxygen was discovered in the coma of comet 67P/Churyumov-Gerasimenko. Its origin was ascribed to primordial gaseous O₂ incorporated into the nucleus during the comet's formation. This thesis was put forward after discounting several O₂ production mechanisms in comets, including photolysis and radiolysis of water, solar wind-surface interactions and gas-phase collisions. Here we report an original Eley-Rideal reaction mechanism, which permits direct O₂ formation in single collisions of energetic water ions with oxidized cometary surface analogues. The reaction proceeds by H₂O⁺ abstracting a surface O-atom, then forming an excited precursor state, which dissociates to produce O₂^-. Subsequent photo-detachment leads to molecular O₂, whose presence in the coma may thus be linked directly to water molecules and their interaction with the solar wind. This abiotic O₂ production mechanism is consistent with reported trends in the 67P coma and raises awareness of the role of energetic negative ions in comets.